1. Field of the Invention
The present invention relates to an optical disk recording and reproducing apparatus for recording and reproducing data in and from an optical disk.
2. Description of the Related Art
In the optical disk recording and reproducing apparatus in which data is recorded in an optical disk and the data recorded in the optical disk is reproduced, a laser beam is focused on a recording surface through a transparent substrate of the optical disk, and high-density data recording and reproduction of the data recorded in high density are realized by micro spots of the laser beam. However, generally warping and deformation exist in the optical disk, which generates a tilt from a normal line between an incident plane and a light beam incident for the recording or reproduction. When the spot is not sufficiently focused on the recording surface due to the disk tilt, reliability is decreased in the recording or reproduction.
A technology in which the decrease in reliability caused by the disk tilt is reduced in the recording or reproduction by performing tilt control is widely known. In the tilt control, a current disk tilt amount is detected to perform compensation according to the disk tilt amount. For example, Japanese Patent Application Laid-Open (JP-A) No. 2000-339731 proposes a technique in which influence of the disk tilt is compensated with an aberration correcting liquid crystal device provided in an optical path. However, in the method disclosed in JP-A No. 2000-339731, there are drawbacks that the liquid crystal device has a low response rate and conventionally the disk tilt amount cannot be detected at high speed.
Thus, a control band of the conventional tilt control method is extremely narrow, and generally static control is performed to an average value of the disk tilt. Accordingly, the control cannot be performed to the disk tilt dynamically changed according to disk rotation, and the reliability of the recording or reproduction is not sufficiently secured.
Therefore, for example, JP-A No. 2001-236666 proposes a technique in which the disk tilt is detected using an optical pickup having plural light beams. In the technique disclosed in JP-A No. 2001-236666, because the disk tilt can be detected in a broadband, broadband control can be performed not lower than a disk rotation frequency by using an objective lens actuator or the like in a tilt compensation unit, so that the reliability of the recording or reproduction can also be secured to the disk tilt dynamically changed according to the disk rotation.
On the other hand, an operation in which the laser spot is moved (jumped) between recording layers or between tracks in the same recording layer is generated during the data recording in the optical disk and the reproduction of the data recorded in the optical disk. During the inter-layer jump and the track jump, there is a possibility that disturbance is generated in a tilt error signal.
In the conventional static disk tilt control, the short-period disturbance has a little influence because the control band is narrow. For example, JP-A No. 2000-339731 proposes a technique in which servo run-away or the like caused by the influence of the disturbance is avoided by holding a tilt drive value during the inter-layer jump and the track jump. In the tilt control method disclosed in JP-A No. 2000-339731, the control band is originally narrow and the short-range track jump and the like are not a target of avoiding method.
However, when the dynamic disk tilt control is performed by the method disclosed in JP-A No. 2001-236666, because the tilt control band is broad, the tilt control follows the disturbance when the disturbance is generated in the tilt error signal during the jump even in the short-range jump. Therefore, the correct compensation is lost, which results in a problem that apparatus operation is destabilized such that the servo run-away is generated during the inter-layer jump and the track jump or abnormal recording and reproduction is generated immediately after the jump.